fix: make @babel/node spawned process bubble msg (#13037)

* Add ipc test

Co-authored-by: Nicolò Ribaudo <nicolo.ribaudo@gmail.com>

packages/babel-node/src/babel-node.js

@@ -96,6 +96,7 @@ getV8Flags(async function (err, v8Flags) {
         }
       });
     });
+    proc.on("message", message => process.send && process.send(message));
     process.on("SIGINT", () => proc.kill("SIGINT"));
   }
 });

packages/babel-node/test/fixtures/misc/child.js

@@ -0,0 +1 @@
+process.send("hello");

packages/babel-node/test/index.js

@@ -0,0 +1,27 @@
+import { spawn } from "child_process";
+import path from "path";
+import { fileURLToPath } from "url";
+
+const dirname = path.dirname(fileURLToPath(import.meta.url));
+const binLoc = path.join(dirname, "../bin/babel-node.js");
+const childLoc = path.join(dirname, "fixtures/misc/child.js");
+
+describe("babel-node", () => {
+  it("ipc works with spawned babel-node process", done => {
+    expect.assertions(1);
+
+    const child = spawn(process.execPath, [binLoc, childLoc], {
+      stdio: ["inherit", "inherit", "inherit", "ipc"],
+    });
+
+    child.on("message", msg => {
+      expect(msg).toBe("hello");
+      done();
+    });
+    child.on("error", error => {
+      console.error(error);
+      done();
+    });
+    child.on("exit", () => done());
+  }, /* timeout */ 20_000);
+});